JP2003332867A - Audio amplifying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an audio amplifying device whose cost can be reduced and which can makes small power consumption by eliminating a multiplier, prevents malfunction and destruction of a delta-sigma modulation circuit by abnormal oscillation, limits the output to a level that is not greater than prescribed and prevents the malfunction and destruction of a class D amplifier circuit by changing the power supply voltage even when an excessive input not lower than prescribed is inputted as an input signal. <P>SOLUTION: A digital sigma modulation circuit 30 applies delta-sigma modulation to the inputted analog signal, and the class D amplifier circuit 4 amplifies the power of a PDM signal subjected to delta-sigma modulation and outputs the resultant PDM signal. An input level detection circuit 21a for detecting the amplitude of an analog input signal and a limiter circuit 21 for limiting the amplitude of the analog input signal to a value that is not higher than prescribed if the amplitude of the analog input signal by the input level detection circuit 21a exceeds the prescribed value are provided on the preceding stage of the digital sigma modulation circuit 30. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound amplification device which is preferably implemented with respect to a signal, inputs an analog sound signal, and records, reproduces and transmits the sound signal as a 1-bit digital signal. is there.

[0002]

2. Description of the Related Art In a conventional delta-sigma modulation circuit 50,
As shown in FIG. 3, a multiplier 52 is interposed between the A / D converter 51 and the subtractor 53. Then, the multiplier 52 controls the amplitude of the input signal by multiplying the input signal by a coefficient so that the maximum value of the input signal input to the subtractor 53 becomes substantially equal to the oscillation limit value.

[0003]

However, the delta-sigma modulation circuit 5 provided in the above-described conventional acoustic amplification device is used.
At 0, the multiplier 52 is provided to control the amplitude component of the input signal to the subtractor 53. This multiplier 52
Is composed of a digital multiplier having a complicated configuration, a microprocessor for controlling the digital multiplier, and the like, and has a problem that the configuration becomes complicated, the cost increases, and the power consumption increases.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to reduce the cost and power consumption by eliminating the multiplier and to make the input signal have a specified value. Even when the above excessive input is input, it prevents malfunction and destruction due to abnormal oscillation of the delta-sigma modulation circuit, limits the output to below the specified value, and malfunctions and destruction of class D amplifier circuit due to change in power supply voltage. An object of the present invention is to provide an acoustic amplification device capable of preventing the above.

[0005]

In order to solve the above-mentioned problems, an acoustic amplification device of the present invention is configured so that an input analog signal is delta-sigma modulated by a delta-sigma modulation means, and this delta-sigma modulated pulse density is used. In an acoustic amplification device that outputs a modulated signal by power amplification by switching, for example, a class D amplifier circuit, and the like, an input signal detection means for detecting the amplitude of the input signal, and an amplitude of the input signal by the input signal detection means have a predetermined value. In the case of exceeding the above, the amplitude limiting means for limiting the amplitude of the input signal to a predetermined value or less is provided before the delta-sigma modulation means.

According to the above invention, the input signal detecting means for detecting the amplitude of the input signal is provided before the delta sigma modulating means, and when the amplitude of the input signal by the input signal detecting means exceeds a predetermined value, the input signal is detected. Amplitude limiting means for limiting the amplitude of the signal to a predetermined value or less is provided. Therefore, in the present invention, the amplitude limitation is applied to the signal input to the digital sigma modulation circuit not in the digital sigma modulation circuit but in the preceding stage.

As a result, by providing the amplitude limiting means in the preceding stage of the digital sigma modulation circuit, even when an over-input signal of a specified value or more is input, malfunction and destruction of the digital sigma modulation circuit are prevented, and the power supply voltage is reduced. Even when is changed, it is possible to prevent malfunction and destruction of, for example, a class D amplifier circuit that amplifies and outputs the power by switching, and controls so as not to output more than a specified value.

Therefore, it is possible to reduce the cost and power consumption by eliminating the multiplier, and malfunction even if the input signal is an excessive input exceeding the specified value due to abnormal oscillation of the delta-sigma modulation circuit. It is possible to provide an acoustic amplification device capable of preventing the destruction, limiting the output to be equal to or less than the specified value, and preventing the malfunction and the destruction of the class D amplifier circuit due to the change of the power supply voltage.

Further, the acoustic amplification device of the present invention is the same as the acoustic amplification device described above, in which, for example, a power supply circuit capable of changing a power supply voltage for power amplification by switching of a class D amplification circuit and the like. Voltage detection means for detecting a change in the power supply voltage, and based on detection of a change in the power supply voltage in the power supply circuit by the voltage detection means, the input signal becomes less than the input limit value of the delta-sigma modulation means, A first signal generating means for limiting the amplitude limiting means to the predetermined value or less is provided.

According to the above invention, since the power supply circuit capable of changing the power supply voltage for power amplification by switching, for example, the class D amplifier circuit is provided, the change in the power supply voltage causes the inside of the digital sigma modulation circuit. The oscillation limit value of changes.

Therefore, in the present invention, the input signal of the delta-sigma modulating means is based on the voltage detecting means for detecting the change of the power supply voltage in the power supply circuit and the detection of the change of the power supply voltage in the power supply circuit by the voltage detecting means. A first signal generating means is provided for limiting the amplitude limiting means to be equal to or less than the predetermined value so as to be less than the input limit value.

For this reason, the first signal generating means causes the amplitude limiting means based on the detection of the change in the power supply voltage in the power supply circuit by the voltage detecting means so that the input is equal to or less than the oscillation limit value of the delta-sigma modulating means. On the other hand, the level of the amplitude value of the input signal is changed to limit it.

Therefore, even when the power supply voltage changes, the level of the amplitude value of the input signal is changed by the amplitude limiting means in the preceding stage of the digital sigma modulation circuit, and the over-input signal of the specified value or more is input. Even in this case, it is possible to prevent the digital sigma modulation circuit from malfunctioning or being destroyed.

The acoustic amplification device of the present invention is the above-described acoustic amplification device, wherein, for example, a power supply circuit capable of changing a power supply voltage for power amplification by switching of a class D amplification circuit and the like, and Voltage detection means for detecting a change in the power supply voltage and detection of a change in the power supply voltage in the power supply circuit by the voltage detection means so that the input signal causes the output of power amplification by the switching to be less than a set value. And a second signal generating means for limiting the amplitude limiting means to the predetermined value or less.

According to the above invention, since the power supply circuit for changing the power supply voltage for power amplification by switching of the class D amplifier circuit is provided, the change of the power supply voltage causes the D-class amplifier circuit to change. The degree of amplification changes.

Therefore, in the present invention, the input signal is switched by the switching based on the voltage detection means for detecting the change of the power supply voltage in the power supply circuit and the detection of the change of the power supply voltage in the power supply circuit by the voltage detection means. A second signal generating means is provided for limiting the amplitude limiting means to the predetermined value or less so that the output of the power amplification becomes less than a set value.

Therefore, in order to keep the output of the class-D amplifier circuit below a predetermined value even when the power supply voltage changes, the second signal generating means is provided with the amplitude limiting means in the preceding stage of the digital sigma modulation circuit. Limit is applied by changing the level of the amplitude value of the signal.

As a result, even if an excessive input signal of a specified value or more is input, it is possible to prevent malfunction and destruction of the class D amplifier circuit and control so that an output of the specified value or more is not output.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The acoustic amplification device 10 of this embodiment is shown in FIG.
As shown in FIG. 1, the input terminal 1, the amplitude limiting section 20, and the digital sigma modulation circuit 30 as the delta sigma modulation means are provided.
A class D amplifier circuit 4, a power supply circuit 5 for supplying a voltage to the class D amplifier circuit 4, and an output terminal 6.

In the digital sigma modulation circuit 30, the analog signal input from the input terminal 1 is passed through the amplitude limiting section 20 and then converted into a digital signal, and delta-sigma modulation is performed, so that high / low 2 is obtained. Pulse density modulated signal expressed by a signal that changes rapidly to a value (hereinafter,
It is called "PDM (Pulse Density Modulator) signal". )
It is converted to and output.

That is, the above digital sigma modulation circuit 3
As shown in FIG. 2, 0 is an A / D converter 31, a subtractor 32, an integrator / adder group 33, a quantizer 34, an output terminal 35, a delay device 36, and a predictor 37. It consists of Thus, in the present embodiment, the A / D converter 31
The multiplier that was conventionally present between the subtractor 32 and the subtractor 32 is omitted.

Further, the predictor 37 is provided with a −Δ register 38a and a + Δ register 38b, and the predictive signal is input to the subtractor 32 by switching the switch 39 according to the polarity of the delay device 36. It is supposed to do.

In the digital sigma modulation circuit 30 described above,
The analog signal input to the A / D converter 31 is
The / D converter 31 converts the analog signal into a digital signal and outputs the digital signal to the subtractor 32. This subtractor 32 has
Predictor 37 based on the delayed signal output from the delay device 36
, The difference between the digital signal and the predicted signal is output from the subtractor 32.

The difference signal output from the subtractor 32 is input to the integrator / adder group 33 and is sigma modulated. Then, the sigma-modulated signal is input to a quantizer 34, and the quantizer 34 is a PDM which is a 1-bit output signal that rapidly changes to the binary value of HIGH / LOW described above.
It is converted into a signal and output. Also, this 1-bit PD
The M signal is fed back to the subtractor 32 by the delay device 36.

Next, as shown in FIG. 1, class D amplifier circuit 4
Is the P output from the digital sigma modulation circuit 30.
A DM signal is input and power switching is performed for power amplification. At this time, the power supply circuit 5 supplies a voltage to the class D amplifier circuit 4. In the present embodiment, the supply voltage of the power supply circuit 5 is variable. Therefore, the magnitude of the output from the class D amplifier circuit 4 can be changed by changing the supply voltage of the power supply circuit 5.

On the other hand, in the present embodiment, as shown in the figure, the amplitude limiting section 20 is provided between the input terminal 1 and the digital sigma modulation circuit 30. That is, the amplitude limiting section 20 is provided in the preceding stage of the digital sigma modulation circuit 30. The amplitude limiter 20 includes an amplitude limiter circuit 21 as an amplitude limiter, a control signal generator 22 and a voltage detector 23 as a voltage detector.

The amplitude limiting circuit 21 has an input level detecting circuit 21a as an input signal detecting means for detecting the level of the input signal.
In response to the output from a, the level of the amplitude value is changed and limited with respect to the analog input signal.

The voltage detector 23 detects the power supply voltage supplied from the power supply circuit 5 to the class D amplifier circuit 4,
The control signal generation circuit 22 controls the amplitude limitation of the amplitude limitation circuit 21.

Here, in this embodiment, two methods are adopted when the amplitude limiting circuit 21 changes the level of the amplitude value to limit the analog input signal.

First, as a first method, the voltage detector 23
Based on the detection of the change in the power supply voltage in the power supply circuit 5 caused by the analog input signal, the analog input signal is changed to the digital sigma modulation circuit 30.
The amplitude limiting circuit 21 is limited to a predetermined value or less so as to be less than the input limit value. It is the control signal generation circuit 22 as the first signal generation means that limits the amplitude limiting circuit 21 to a predetermined value or less.

In the second method, based on the detection of the change in the power supply voltage in the power supply circuit 5 by the voltage detector 23, the analog input signal indicates that the output of the power amplification by the class D amplifier circuit 4 is less than the set value. So that the amplitude limiting circuit 21
Is limited to a predetermined value or less. It is the control signal generation circuit 22 as the second signal generation means that limits the amplitude limiting circuit 21 to a predetermined value or less.

As a result, even if an analog input signal of a specified value or more is input, or if the power supply voltage changes, a signal of the specified value or more is not input to the digital sigma modulation circuit 30. Therefore, it is possible to prevent malfunction and destruction of the digital sigma modulation circuit 30. Also, since there is no excessive input, the problem of increased power consumption is eliminated.

As described above, in the acoustic amplification device 10 of the present embodiment, the input level detection circuit 21a for detecting the amplitude of the analog input signal is provided in the preceding stage of the delta-sigma modulation means.
An amplitude limiting circuit 21 is provided for limiting the amplitude of the analog input signal to a predetermined value or less when the amplitude of the analog input signal by the input level detection circuit 21a exceeds a predetermined value. Therefore, in the present embodiment, the amplitude limitation is applied to the signal input to the digital sigma modulation circuit 30 not in the digital sigma modulation circuit 30 but in the preceding stage.

As a result, by providing the amplitude limiting circuit 21 in the preceding stage of the digital sigma modulation circuit 30, even if an over-input signal of a specified value or more is input, malfunction and destruction of the digital sigma modulation circuit 30 can be prevented. Even when the power supply voltage changes, it is possible to prevent malfunction and destruction of the class D amplifier circuit 4 that amplifies and outputs the power by switching, and controls so as not to output more than the specified value.

Therefore, the cost and power consumption can be reduced by eliminating the multiplier, and the abnormal oscillation of the digital sigma modulation circuit 30 can be achieved even when the analog input signal is over-input more than the specified value. It is possible to provide the acoustic amplification device 10 capable of preventing the malfunction and destruction due to the above, limiting the output to the specified value or less, and preventing the malfunction and the destruction of the class D amplifier circuit 4 due to the change of the power supply voltage.

Further, since the acoustic amplification device 10 of the present embodiment is provided with the power supply circuit 5 capable of changing the power supply voltage for power amplification by switching the class D amplification circuit 4 or the like, Due to the change, the oscillation limit value inside the digital sigma modulation circuit 30 changes.

Therefore, in this embodiment, an analog input signal is detected based on the voltage detector 23 for detecting the change in the power supply voltage in the power supply circuit 5 and the detection of the change in the power supply voltage in the power supply circuit 5 by the voltage detector 23. Is provided below the input limit value of the digital sigma modulation circuit 30, a control signal generation circuit 22 for limiting the amplitude limiting circuit 21 to a predetermined value or less.

For this reason, the control signal generation circuit 22 detects the change of the power supply voltage in the power supply circuit 5 by the voltage detector 23 so that the input becomes less than the oscillation limit value of the digital sigma modulation circuit 30. Limit circuit 2
With respect to 1, the level of the amplitude value of the analog input signal is changed to limit it.

Therefore, even when the power supply voltage changes, the amplitude limiter circuit 21 changes the level of the amplitude value of the analog input signal in the preceding stage of the digital sigma modulation circuit 30 to input an over-input signal of a specified value or more. Even in the case of being caused, it is possible to prevent the digital sigma modulation circuit 30 from malfunctioning or being destroyed.

Further, in the acoustic amplification device 10 of the present embodiment, since the power supply circuit 5 capable of changing the power supply voltage for power amplification by switching the class D amplification circuit 4 or the like is provided, the power supply voltage of this power supply voltage Class D amplifier circuit 4 due to changes
The amplification degree of changes.

Therefore, in the present embodiment, the analog input signal is detected based on the power supply circuit 5 for detecting the change in the power supply voltage in the power supply circuit 5 and the change in the power supply voltage in the power supply circuit 5 detected by the voltage detector 23. However, a control signal generation circuit 22 for limiting the amplitude limiting circuit 21 to the predetermined value or less is provided so that the output of power amplification by switching of the class D amplifier circuit 4 or the like becomes less than a set value.

Therefore, in order to keep the output of the class D amplifier circuit 4 below a predetermined value even when the power supply voltage changes,
In the preceding stage of the digital sigma modulation circuit 30, the control signal generation circuit 22 causes the amplitude limiting circuit 21 to change the level of the amplitude value of the analog input signal to limit it.

As a result, even when an over-input signal of a specified value or more is input, it is possible to prevent malfunction and destruction of the class D amplifier circuit 4 and control so that an output of the specified value or more is not output.

[0045]

As described above, the acoustic amplification apparatus of the present invention is provided with the input signal detecting means for detecting the amplitude of the input signal, and when the amplitude of the input signal by the input signal detecting means exceeds a predetermined value. Amplitude limiting means for limiting the amplitude of the input signal to a predetermined value or less is provided before the delta-sigma modulation means.

Therefore, by providing the amplitude limiting means in the preceding stage of the digital sigma modulation circuit, even when an over-input signal of a specified value or more is input, malfunction and destruction of the digital sigma modulation circuit are prevented, and the power supply voltage is reduced. Even when is changed, it is possible to prevent malfunction and destruction of, for example, a class D amplifier circuit that amplifies and outputs the power by switching, and controls so as not to output more than a specified value.

Therefore, it is possible to reduce the cost and power consumption by eliminating the multiplier, and even if the input signal is an excessive input of a specified value or more, malfunction due to abnormal oscillation of the delta-sigma modulation circuit. Thus, it is possible to provide an acoustic amplification device capable of preventing the destruction, limiting the output to the specified value or less, and preventing the malfunction and the destruction of the class D amplifier circuit due to the change of the power supply voltage.

Further, the acoustic amplification device of the present invention is, in the acoustic amplification device described above, a power supply circuit capable of changing a power supply voltage for power amplification by switching, and a voltage for detecting a change in the power supply voltage in the power supply circuit. Based on the detection means and the detection of the change of the power supply voltage in the power supply circuit by the voltage detection means, the predetermined value is given to the amplitude limiting means so that the input signal becomes less than the input limit value of the delta-sigma modulation means. And a first signal generating means for limiting the value to a value or less.

Therefore, the first signal generating means causes the amplitude limiting means to operate on the basis of the detection of the change in the power supply voltage in the power supply circuit by the voltage detecting means so that the input is less than the oscillation limit value of the delta-sigma modulating means. On the other hand, the level of the amplitude value of the input signal is changed to limit it.

Therefore, even when the power supply voltage changes, the level of the amplitude value of the input signal is changed by the amplitude limiting means in the preceding stage of the digital sigma modulation circuit, and the over-input signal of the specified value or more is input. Even in such a case, it is possible to prevent the digital sigma modulation circuit from malfunctioning or being destroyed.

The acoustic amplification device of the present invention is, in the acoustic amplification device described above, a power supply circuit capable of changing a power supply voltage for power amplification by switching, and a voltage for detecting a change in the power supply voltage in the power supply circuit. Based on the detection means and the detection of the change in the power supply voltage in the power supply circuit by the voltage detection means, the input signal is supplied to the amplitude limiting means such that the output of the power amplification by the switching becomes less than a set value. Second signal generating means for limiting the value to the predetermined value or less.

Therefore, even when the power supply voltage changes,
In order to reduce the output of the class D amplifier circuit to a predetermined value or less, the second signal generating means, before the digital sigma modulation circuit, causes the amplitude limiting means to change and limit the amplitude value of the input signal.

As a result, it is possible to prevent malfunction and destruction of the class D amplifier circuit even when an over-input signal of a specified value or more is input, and control so that an output of a specified value or more is not output.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an acoustic amplification device according to the present invention.

FIG. 2 is a block diagram showing an electrical configuration of a digital sigma modulation circuit in the acoustic amplification device.

FIG. 3 is a block diagram showing an electrical configuration of a conventional digital sigma modulation circuit.

[Explanation of symbols]

4 Class D Amplifier Circuit 5 Power Supply Circuit 6 Output Terminal 10 Acoustic Amplifier 20 Amplitude Limiting Unit 21 Amplitude Limiting Circuit (Amplitude Limiting Means) 21a Input Level Detecting Circuit (Input Signal Detecting Means) 22 Control Signal Generating Circuit (First Signal Generating Means) , Second signal generation means) 23 voltage detector (voltage detection means) 30 digital sigma modulation circuit (delta sigma modulation means) 31 A / D converter 32 subtractor 33 integrator / adder group 34 quantizer 35 delayer 37 Predictor

Continued front page    F-term (reference) 5D020 AC01                 5J030 CB03 CC00                 5J064 AA00 BA03 BC00 BC04 BC06                       BC08 BC10 BC16 BC19 BC30                       BD01                 5J091 AA02 AA41 AA66 CA36 CA54                       CA56 CA87 FA01 HA38 KA00                       KA15 KA20 KA26 KA31 KA33                       KA34 KA47 KA53 MA21 SA05                       TA01 UW01

Claims (3)

[Claims] 1. An acoustic amplification device for delta-sigma modulating an input analog signal by delta-sigma modulation means, and power-amplifying and outputting the delta-sigma modulated pulse density modulated signal by switching. The delta-sigma modulating means includes an input signal detecting means for detecting an amplitude and an amplitude limiting means for limiting the amplitude of the input signal to a predetermined value or less when the amplitude of the input signal by the input signal detecting means exceeds a predetermined value. An acoustic amplification device characterized by being provided in the preceding stage. 2. A power supply circuit capable of changing a power supply voltage for power amplification by the switching, a voltage detection means for detecting a change of the power supply voltage in the power supply circuit, and a power supply voltage in the power supply circuit by the voltage detection means. A first signal generating means for limiting the amplitude limiting means to the predetermined value or less so that the input signal becomes less than the input limit value of the delta-sigma modulating means based on the detection of the change. The acoustic amplification device according to claim 1, wherein 3. A power supply circuit capable of changing a power supply voltage for power amplification by the switching, a voltage detection means for detecting a change in the power supply voltage in the power supply circuit, and a power supply voltage in the power supply circuit by the voltage detection means. And a second signal generating means for limiting the amplitude limiting means to the predetermined value or less so that the output of the power amplification by the switching becomes less than a set value based on the detection of the change. The acoustic amplification device according to claim 1, wherein